Babies which are born after about a 10 week gestation period typically are capable of functioning independently of the mother from a hormonal standpoint, and at this stage the only maternal functions are to supply oxygen and nutrients to the fetus and to remove waste byproducts such as uric acid. However, until about 28 weeks, lungs are not sufficiently developed to support the baby; consequently, babies born before ; the 28th week of gestation, as by irreversible premature labor, have little chance to survive.